I use them at home and when I travel. I also find that they aren't as good as they used to be. Some of my favorite local restaurants sell out quick, then drop from restaurant.com completely. When I travel, will search for places before and purchase if I know I'll have an opportunity to visit the restaurant. Also, I will purchase the cert at my hotel and use their printer to print it out.

I usually find an additional discount for that will get me a $25 cert for $3-4.

I have also had good success at getting certificates refunded (credit in my account) if I wasn't able to use the certificate. Once the restaurant/bar stopped serving dinner early (due to snow storm/low traffic) and restaurant.com refunded. Another time a local restaurant was closed for the week when I was traveling (Gone Fishing on the door) and I got the refund.

Just watch for the minimum purchase and days of usage (some exclude Fri/Sat).